Polar bivalves are characterized by high antioxidant defences

Inevitably, aerobic life leads to the formation of deleterious reactive oxygen species (ROS) which participate in biomolecule oxidation, hence augmenting biomolecule turnover. Organisms have adapted to counteract the noxious effects of ROS by developing a battery of antioxidant defences (AOX) which comprise enzymes and low-molecular weight scavengers. Past studies have reported elevated AOX levels in polar pectinid bivalves compared with temperate congeners. This finding is controversial as mitochondrial ROS generation is low in polar versus temperate species, and, to date, there is no generally accepted explanation of the causes of increased basal AOX levels in polar waters. We suggest that the low food availability in those ecosystems may result in polar marine ectotherms diverting some energy into the maintenance of high AOX. We tested this hypothesis by comparing the total oxyradical scavenging capacity (peroxyl, hydroxyl and peroxynitrite) of three clam species: Laternula elliptica (Antarctic), Mya truncata (Arctic) and Mya arenaria (temperate). The data confirmed that polar bivalves are characterized by higher AOX. Herein, we propose that high AOX is required in environments characterized by low food availability as AOX efficiently protects biomolecules, notably the RNA expressed at high levels by cold-water ectotherms. Also, high AOX may explain the relatively long lifespan of most polar ectotherms.     

Flushing times for the Providence River based on tracer experiments

The flushing time of the Providence River was estimated using three different data sets and three different methodologies. Dye concentrations were measured following instantaneous dye releases during wet weather experiments performed by the Narragansett Bay Project between October 1988 and June 1989. These data were analyzed to obtain flushing time estimates. Salinity measurements collected during the Sinbadd (Sampling In Narragansett Bay All During the Day) cruises, Spray (Sampling the Providence River All Year) cruises and wet weather experiments were used with the fraction of fresh water method and box model to calculate flushing time. The Sinbadd cruises performed 4 seasonal surveys at 22 stations in Narragansett Bay during 1986 to obtain a view of the whole Narragansett Bay with respect to the concentrations of nutrients and trace metals. The Spray cruises collected data in the Providence River at 10 stations to determine the relationship of nutrients and trace metals concentrations in the Seekonk and Providence rivers as a function of point source inputs. Based on the flushing time estimates, an exponential relationship between freshwater inflow and flushing time was developed (correlation coefficient of 0.826). The flushing time ranged from 0.8 d at high (90 m³ m^?1) freshwater inflows to 4.4 d at low (20 m³ s^?1) freshwater inflows. The average flushing time of the Providence River was estimated as 2.5 d for the mean freshwater inflow of 42.3 m³ s^?1.     

Soil and stream sediment geochemical dispersion over the Bell Springs deposit, Hog Ranch Mine, Washoe County, Nevada

The Bell Springs deposit is a bulk-tonnage, low-grade gold deposit, formed in a hot-spring environment, that is hosted by middle Miocene weakly peralkaline, high-silica rhyolite ash flows and rheomorphic tuffs. Ore grade mineralization over about 460 × 460 m was controlled by northeast- and northwest-trending structures. Sixty-nine soil samples collected along a traverse across the Bell Springs deposit, screened into six mesh size fractions, +10, −10+35, −35+80, −80+120, −120+200, and −200, were treated by low-detection-limit acid digestion/organic extraction procedures, and analyzed by ICP or graphite furnace techniques for Au, Ag, As, Bi, Cd, Cu, Ga, Hg, Mo, Pb, Sb, Se, Te, Tl, and Zn. Twenty-five stream-sediment samples were collected from a drainage crossing mineralization and from a nearby tributary. Sediment size fractions of −200 mesh and −10+200 mesh were analyzed by the same procedures used for soils. In addition, analyses of bulk leachable gold via cyanide leach method (BLEG) was done on bulk −10 mesh sediments.Anomalous Au, Ag, As, Sb, and Mo in all soil size fractions revealed the underlying ore. Areas with anomalous Sb and As were about three times larger than areas with anomalous Au and Ag. Analyses of fine-fractions of stream sediments provided the best-defined Au anomalies in drainages. A multi-element factor calculated by multiplying Au, As, Sb, and Mo reinforced anomalous Au in drainages and correlated well with Bell Springs mineralization.     

Depositional process and alluvial fan-drainage basin morphometric relationships near banff,Alberta, Canada

Two distinct types of alluvial fans occur in the Bow River Valley, Alberta, Canada: fluvially dominated and debris flow dominated. Large, gently sloping fans dominated by fluvial processes are associated with large and less rugged drainage basins, and small rugged basins have produced small, steep fans dominated by debris flow processes. Quantitative analysis demonstrates that strong fan-basin morphometric relationships occur despite a short fan history. Statistical analysis of fan area-basin area relationships indicate that debris flow fan areas do not increase in size as quickly as contributing basins. The relationship of fluvial fan area to basin area is not statistically significant. However, this relationship is probably affected by fan erosion. Examination of fan slope to basin ruggedness relationships indicates that fan slope increases more rapidly than basin ruggedness for both fan types. This is likely related to non-linear discharge and sediment size effects on fluvial fans, and reworking of larger fan surfaces by fluvial processes on debris flow fans.     

Retention and release of methane in underground coal workings

Summary During an investigation to study the gas flow characteristics of coal, adsorption and desorption rates of methane from powdered coal samples were measured. From adsorption tests, it was found that the capacity of coal to hold methane varies significantly with gas pressure. For pressures up to 4.14 MPa (600 psi) the amount of gas adsorbed was still rising and monomolecular saturation was not reached. Results of desorption tests were used to test three equations suggested by previous investigators to measure the quantity of desorbed gas. It was confirmed that no single equation would define adequately the complete desorption process. Changes of regime appeared to exist at desorption times of 100 s and, to a lesser extent, 1000 s following the initial release of ambient gas pressure. A hypothesis was advanced that initial flow was inhibited or choked by an efflux of desorbing gas molecules. This was followed by a short transitional period and a longer term regime of free flow with reduced resistance offered by the flow paths.     

Magnetovariational measurements in the Cook Strait region of New Zealand

Magnetovariational measurements have been made at 10 sites on the northern side of the Cook Strait, New Zealand. Single-station transfer functions have been calculated for the sites and indicate that the effect of induction in the shallow water of the Cook Strait is most important at around 1000 s period. At longer periods the effect of induced currents in the Pacific Ocean predominates.A two-dimensional electrical conductivity model including local conductivity structure has been shown to satisfy the measured responses at sites about 60–80 km distance from the strait. Closer to the strait the inductive process is strongly three-dimensional. A simple d.c. line current model of current flow has been shown to reproduce some of the features of the observed responses.Induction arrows indicate the existence of conductivity anomalies associated with a known lateral seismic boundary and with one of the two principal faults in the region.     

Comparing tiltmeters for crustal deformation measurement--a preliminary report

A collection of high-precision tiltmeters is being operated at Pinon Flat Observatory, southern California, both to compare instruments and to measure tectonic deformation. We report on 1.2 years of data from four of these: two Michelson-Gale long fluid tiltmeters, one long center-pressure tiltmeter, and a shallow borehole tiltmeter. The three long-base instruments are all located on the same baseline, with a precise leveling line running between their end-monuments. At nontidal frequencies, only the two Michelson-Gale instruments show some coherence (gamma 2 = .3 for periods of 2 to 4 days), while the center-pressure instrument is correlated with air temperature at periods from a few days to a few weeks. The most stable tilt record shows a secular rate of 0.28 mu rad/a, which may be real. Over much longer times, leveling to specially stabilized bench-marks should confirm this. Comparing instruments has identified more and less successful measurement techniques; it appears that low-noise data will most probably be produced only by relatively complex and expensive instruments, though even for these, the operating costs over any reasonable lifetime will exceed the capital cost. Even the best existing sensors must be improved to measure continuous tectonic motions.     

The central Kenya peralkaline province: Insights into the evolution of peralkaline salic magmas

The central Kenya peralkaline province comprises five young (< 1 Ma) volcanic complexes dominated by peralkaline trachytes and rhyolites. The geological and geochemical evolution of each complex is described and issues related to the development of peralkalinity in salic magmas are highlighted. The peralkaline trachytes may have formed by fractionation of basaltic magma via metaluminous trachyte and in turn generated pantellerite by the same mechanism. Comenditic rhyolites are thought to have formed by volatile-induced crustal anatexis and may themselves have been parental to pantelleritic melts by crystal fractionation. The rhyolites record very low temperatures of equilibration (≤ 700 °C) at low fO₂ (≤ FMQ). The development of compositional zonation within the magma reservoirs has been ubiquitous, involving up to tens of cubic km of magma at timescales of 10³–10⁴ years. Magma mixing has also been commonplace, sometimes between adjacent centres. Isotopic evidence relating to rates and timescales of pre-eruptive residence times and crystal fractionation processes is summarized.     

The influence of geological fabric and scale on drainage pattern analysis in a catchment of metamorphic terrain: Laceys Creek, southeast Queensland, Australia

The relationship between geological fabric and drainage patterns in the 81.8 km² Laceys Creek sub-catchment of the North Pine River catchment, southeast Queensland, Australia, is analysed using a new channel–ordination system. The Laceys Creek catchment is situated on the South D'Aguilar Block, which underwent metamorphism, faulting and uplift from the Late Carboniferous to Late Triassic. The catchment drains exposures of two main rock units, the Neranleigh–Fernvale Beds and the Bunya Phyllite. Both units are composed of metamorphosed deep-sea sediments that accumulated as an accretionary wedge during late Palaeozoic subduction of the palaeo-Pacific plate under the eastern margin of the Australian craton. The new channel ordination system used in this study allows improved classification of stream segments of equal prominence or rank in comparison to previous schemes. A 10 m contour digital elevation model (DEM) was produced within which drainage channels were digitised. Planar geological features, including bedding, faults, joints and cleavage, were mapped in the field and collated with data from previous geological mapping programs.Regional and local trends of geological fabric are reflected in the variable orientation of channels of different rank in the catchment. Cleavage and fractures are the dominant planar features of the Bunya Phyllite and these correlate most closely with the orientation of middle-order incised stream segments. In contrast, middle-order channels on the Neranleigh–Fernvale Beds most closely correlate with bedding, which dominates the fabric of this unit. Although anthropogenic factors exert local influence and climatic processes exert broad influence on the catchment, this study focuses on structural and lithological fabrics, which are the apparent dominant controls on middle-order channel orientations. Identification of congruent patterns between bedrock fabric and channel ranks is variable, depending on the scale and number of channels included in the analysis. Many low-rank channels correspond closely to the orientation of fine-scale bedding and foliation and these influences may not be detected by coarse-scale mapping. Understanding the extent of geological controls on the morphology of a catchment may assist geo-hazard identification, land-use planning and civil-engineering projects.